Repartitioning in Windows 7 is usually fairly straight forward. There is always a chance of repartitioning causing problems, but it almost always works fine, and is rarely the cause of system crashes when done properly. Just in case, you may want to make a backup of any particularly important files.
What exactly are you trying to do? If you want to create a new partition, you'll first have to shrink your existing one. It is advisable to defragment your drive before resizing. You can do this by typing
disk defrag into the start menu and selecting the disk defragmenter. Once you're ready to do the resizing:
- Open the disk manager, by running
- Your hard drive should be selected. You may see only one partition, likely the
C: drive, or you may see a few others, such as a built-in recovery partition.
- Select the partition you want to resize. This will likely be the biggest one; probably the
- Right-click and choose "Shrink volume". Choose how much smaller you want to make it.
- In the new empty space, right-click and choose "New simple volume". Format it with NTFS, name it, and assign it a drive letter.
- Wait for the format to complete. Once this is done, your new partition should be ready to go.
Once you have done this, you should have two partitions on your drive. If you wanted to repartition so you could install a second OS or something like that, you may need to make some other configurations, but this should be enough to get you going.
Repartitioning rarely causes errors. Be certain however that you have a reliable power source while resizing - I was once in the midst of moving (a more complicated, risky operation) a partition when the power went out. The data on that disk was a complete loss, almost every file was corrupted, but fortunately I had backups. I've never had a problem just shrinking, but making a backup can never hurt.